The present invention relates to hydraulic units of the bent axis type. More particularly, this invention relates to a swinging yoke type bent axis hydraulic unit.
Bent axis hydraulic units have been known for many years. The most widespread or common of the bent axis designs utilizes a "tilting block" such as disclosed by Forster in U.S. Pat. No. 4,893,549. A rotatable cylindrical drum or cylinder block kit has a plurality of axial pistons therein supported on a nonrotatable swivel carriage on its axis of rotation. The swivel carriage has a convex end face positioned against a concave swivel carriage guide surface. The swivel carriage guide surface is part of the swivel carriage housing, which is attached to the machine.
Other bent axis units utilize a "swinging yoke" configuration. The cylinder block kit is carried by the yoke and swings with it to vary the displacement of the unit.
A control mechanism of the prior applications includes a stepper motor, control member with an elongated bore, an elongated hydraulic fluid control spool movably mounted in the bore and positioned by the cooperative functions of the stepper motor and the feedback signal to the spool which senses a cam on a pivotal yoke, and a pair of servo pistons operatively mechanically connected to the yoke and hydraulically connected to the fluid control spool.
The principal object of this invention is to replace the stepper motor with a proportional solenoid fluid valve which is operatively connected to a computer.
A further object of this invention is to have one end of the fluid control spool influenced by the solenoid fluid valve, and the other end influenced by a spring loaded feedback system operatively connected to the yoke or pivotal member of the system.
These and other objects will be apparent to those skilled in the art.